Photochemical manufacture of 1,1,1-difluorochloroethane



Patented Mar. 7, 195% PHOTOCHEMICAL MANUFACTURE OFLLI-DIFLUOROCHLOROETHANE John D. Calfee, Manhasset, N. Y., and Lee B.Smith, Woodbridge, N. J., assignors to Allied Chemical & DyeCorporation, a corporation of New York No Drawing. Application March 16,1946, Serial No. 655,012

4 Claims. (Cl. 204163) This invention relates to manufacture of1,1,1-difluorochloroalkanes such as 1,1,l-difluorochloroethane,CH3CF2C1, a non-toxic, moderately flammable gas (B. P. minus 9.6" C.)especially useful as a refrigerant and as an intermediate in otherprocesses. The present improvements are herein described in connectionwith the chlorination of ethylidene fluoride, CH3CHF2, to form1,1,1-difluorochloroethane.

It has been proposed to make fluoro and fluorohalo aliphatichydrocarbons by reacting halogenated aliphatic hydrocarbons, containinghalogen other than fluorine, with a flucrinating agent such as antimonytrifluoride, and several fluoro and fluorohalo derivatives of aliphatichydrocarbons have been prepared by this general method. I-Ienne et al.report (J. Am. Chem. Soc, 58, 889, 1936) preparation of1,1,l-difluorochloroethane in accordancewith the foregoing principlesusing 1,1,1-trichloroethane as the halogenated hydrocarbon and antimonytrifiuoride in the presence of an antimony pentahalide as fluorinatingagent. These procedures have the marked disadvantages of inherent sidereactions which include splitting out of HP from the starting material.Further, it is well known in the chlorination art in general that thecommercially important disadvantage lies in the fact that the amount ofthe monochlorinated material produced is extremely low because of theunavoidable formation of large amounts of polychlorinated side reactionproducts. Hence, prior art knowledge points away from the possibility ofeffecting commercially satisfactory mono chlorination of 1,1difluoroalkanes such as ethylidene fluoride to introduce a chlorine atominto the carbon atom already bearing the two fluorine atoms. 7

The principal object of this invention is provision of processes bypractice of which it is possible to obtain high commerciallysatisfactory yields of 1,1,1-difiuorochloroalkane derivatives of1,1-difluoroalkanes such as ethylidene fluoride.

Applied to the manufacture Of1,1,1,dlfllll0 chloroethane, practice ofthe invention involves effecting reaction of ethylidene fluoride andchlorine by actinic radiation.

The reaction taking place may be represented by the following equation--Essentially, this reaction is a substitution halogenation of a1,1-dihalo derivative of a saturated aliphatic hydrocarbon.

This invention is based on the discovery that when ethylidene fluorideand not substantially more than one molecular proportion of chlorine aresubjected to the action of actinic radiation (to the action of any lightwhich effects chemical change) there is substantially immediatelyproduced a gaseous reaction mixture comprising a recoverable mixture ofreacted materials containing by weight a predominating amount of1,1,1-difluorochloroethane. Under moderately favorable conditions ofoperation, such recoverable mixtures of reacted materials contain byWeight not less than 80%, usually about 80-95% of1,1,1-difiuorochloroethane, and yields of the desired monochlorinatedproduct are and higher. The term yield is used herein to denote thepercent by weight of ethylidene fluoride input which is recovered as1,1,1-difluorochloroethane.

We have discovered that the foregoing is true whether the reaction iseffected in the presence of substantially less than one, one, or notsubstantially more than one molecular proportion of chlorine. Theinvention comprises the discovery of this inherent reactioncharacteristic which is surprisingly distinguishable from theexpectation that chlorination would proceed, as indicated by the priorart, to formation of a predominating amount of polychlorinated endproducts. Also, it is surprising that the recoverable product should bealmost exclusively the 1,1,1-compound rather than a mixture of the1,1,1- and 1,1,2-isomers. Further, we flnd that the resulting reactionmixture is relatively stable and that the contained1,1,1-difluorochloroethane is recoverable as such by commerciallyfeasible methods without the taking place of further chlorination andits attendant production of further amounts of polychlorinated or otherundesirable side reaction products.

Applied to manufacture of 1,1,1-difluorochloroethane, the inventionparticularly comprises subjecting a mixture of ethylidene fluoride andnot substantially more than one molecular proportion of chlorine to theaction of actinic radiation, and recovering a mixture of reactedmaterials containing by weight a predominating amount, usually and up,of 1,1,1-difluorochloroethane.

We have found that recovery of the mixture of reacted materialscontaining maximum quantities of the desired monochlorinated derivativeand minimum quantities of polychlorinated and other undesirable sidereaction products may be had easily by regulating the amount of chlorinepresent in the reaction to not substantially more than tinuous operationin which chlorine and ethylidene fluoride are continuously introducedinto a reaction zone, subjected therein to the action of actinicradiation, and the resulting reaction mixture continuously dischargedfrom the reaction zone, a specific discovery of the invention being thatwhen the indicated proportions of raw materials are continuouslyintroduced into a reaction zone, subjected to the action of actinicradiation therein, and the resulting reaction mixture continuouslydischarged, there is formed a reac tion zone gaseous efiluent comprisinga mixture of reacted materials containing by weighta pre' dominatingamount, usually 80% and up, of 1,1,1

difiuorochloroethane.

The reaction may be carried out conveniently by passing the startingmaterials into and thru a glass enclosed reaction space, such as theannular space formed bysurrounding a fluorescent light tube with a glasstube of larger diameter.

Any form of light which efiects chemical reaction of the reaction. Spacevelocity per hour should be preferably not more than 600 and ordinarilyin the range of 200 to 300. In the preferred em.- bodiments of theinvention, approximately one molecular proportion of chlorine isemployed. When so proceeding, practically all of the chlorine isutilized in the reaction, and the amount of (51110? rine escaping thereaction zone is so small that disposal of such unreacted chlorine towasteafiords no economic disadvantage. The reaction is exothermicalthough not highly so. In most operations, particularly usingfluorescent light, temperature control of the reactors has'beenunnecessary, since temperatures automatically maintain themselves withinthe range from about room temperature to about 300 C. Should operationsbe of such character as to develop undue amounts of heat, any suitablecooling means to keep temperature below about 300 C. may be employed.The reaction proceeds in the presence of any amount of actinicradiation, although the speed of reaction appears to be directlyproportional to the intensity of light. We find that oxygen inhibits thechlorination reaction, and in practice the process is carried out underconditions such that the reaction is effected in the presence'of lessthan 0.1% by weight of oxygen based on the amount of ethylidene fluoridecharged.

Exit gases from the reactor may be purified and the sought-for1,1,1-difluorochloroethane recovered in any satisfactorymanner. Forexample, the efiluent of the reactor may be passed first thru a waterscrubber which removes from the gas stream most of the H01, then thru ascrubber which may contain a suitable aqueous caustic soda solution, e.g. one having an NaOI-I strength in the range of 10 to In this scrubberthe unreacted chlorine and the last traces of HCl are removed from thegas stream. Thereafter, the gas may be passed thru a suitable dryer suchas a column of silica gel or calcium chloride. There is thus produced agas stream which contains principally CI-IzCFzCl, unreacted CHsCI-IFz,and some CH2C1CHF2, CHzCICFzCl, and CHClzCI-IFz. The constituents ofthis gas may be totally liquefied in a suitable receiver b cooling towell below minus 24.? C., the boiling point of ethylidene fluoride. Thereceiver may be transferred .to a still, temperature of liquid raised toabout minus 24-25 C. to distill off the CHaCI-IFz which may be recycledto the reactor. The residual liquid in the still is a mixture of reactedmaterials which mixture, as indicated by the following examples, maycontain 8l-921% by weight of 1.1.1rdifluorochloroethane.

The temperature of the liquid in the still may be raised sufliciently todistill on" an overhead which, when condensed is a liquid having aboiling point of minus C. i 0.5 C., i. e. the soughtefor1,1,1edifluorochloroethane product. This leaves in the still, a residuecomprising chiefly CHzClCI-IFz, boiling at about 35 0., CHzClCFzClboiling at about 47 0., and CHCl2CI-IF2 boiling .at about 60 'C. Thestill residue may also contain relatively small amounts of otherpolych'lorinated products all of which have boiling points above about60 .C.

In the following examples all parts, are parts by weight, and the termyield is used to desighate the percent byweight of ethylidene fluorideinput which was recovered as 1,1,1-difi1iorochloroethane. In allinstances the ethylidene fluoride and chlorine were fed into thereactors at room temperature and at pressure sufiicientl aboveatmospheric to force the gases thru the train of apparatus. Temperaturesin all examples were less than about 300 C. and were generally in therange of =250 C.

cmrl 1 A feed gas mixtureconsisting of 77 parts of ethylidene fluorideand 43 parts of chlorine was fed continuously into one end of a tubulartransparent quartz reactor 10" long and having an inside diameter of 1%,the reactor and the mixture therein being exposed to thelight generatedby an adjacent mercury arc. The ethylidene fluoride andthe chlorine werefed i to the reactor at the respective rates of 0.00629 and 0.00346cubic foot per minute, and rate of flow oi the gas mixture thru thereactorwas about 42 space velocity per hour. Molecular proportions ofethylidene fluoride to chlorine actually passed thru the reactorthroughout the run were one to 0.55. The reaction was exothermic, heatwas generated, but no extraneous cooling was used. The reactor gasmixture was continuously discharged from the reactor and was bubbledthru water to remove most of the HCl, then bubbled thru a caustic sodasolution of NaOH strength of about 20% to remove unreacted chlorine andthe last traces of HCl, and the gas stream was thereafter dried bypassing the same thru a column of calcium chloride. Following theseoperations, the gas stream was passed into a receiver packed in amixture of dry ice and a little acetone to facilitate heat transfer.Gaseous constituents of the gas stream were condensed at temperature ofabout minus 78 C. AtIthe end ofthe run, the receiver was transferred toa fractioning still, and the temperature of the liquid material wasraised to about minus 25 C. Overhead distillate was condensed and therewere recovered 35.1 parts of material having a boiling point of aboutminus 24-25 C., recognized boiling point of ethylidene fluoride beingminus 24.5 C. Temperature of the residual liquid in the still was thenraised to about minus C. Overhead distillate was condensed and therewere recovered 35.7 parts of condensate having a boiling point in therange of minus 9 to 10 C., recognized boiling point of1,1,1-difluorochloroethane being minus 9.6 C. The yield of1,1,l-difluorochloroethane was about 30.4%.

Example 2 A feed gas mixture consisting of 101 parts of ethylidenefluoride and 37 parts of chlorine was fed continuously into one end of atubular Pyrex glass reactor 10 long and having an inside diameter of1%", the reactor and the mixture therein being exposed to the lightgenerated by an adjacent 300 watt tungsten lamp ina reflector. A lightreflector was placed adjacent the reactor diametrically opposite thelamp. The ethylidene fluoride and the chlorine were fed into the reactorat the respective rates of 0.00629 and 0.00213 cubic foot per minute,and rate of flow of the gas mixture thru the reactor was about 65 spacevelocity per hour. Molecular proportions of ethylidene fluoride tochlorine actually passed thru the reactor throughout the run were one to0.34. The reaction was exothermic, heat was generated, but no extraneouscooling was used. The reacted gas mixture was continuously dischargedfrom the reactor and was bubbled thru water to remove most of the H01.The gas stream was passed into a first receiver packed in a mixture ofdry ice and a little acetone. The gaseous constituents of the gas streamwere condensed at temperature of about minus 78 C. At the end of therun, the receiver was transferred to a still, and the liquid content ofthe receiver completely vaporized. The resulting vapor was bubbled thrua caustic soda solution of NaOH strength of about to remove unreactedchlorine and the last traces of HCl, and the gas stream was thereafterdried by passing the same thru a column of calcium chloride. Followingthese operations, the gas stream was passed into a second receiverpacked in a mixture of dry ice and a little acetone. Gaseousconstituents of the gas stream were condensed at temperature of aboutminus '7 8 C. The second receiver was transferred to a fractionatingstill, and the temperature of the liquid material was raised to aboutminus C. Overhead distillate was condensed and there were recovered 25.8parts of material having a boiling point of about minus 2425 C., i.eethylidene fluoride. Temperature of the residual liquid in the still wasthen raised to about minus 10 C. Overhead distillate was condensed andthere were recovered 13 parts of condensate having a boiling point inthe range of minus 9 to 10 C., i.e. 1,1,1- difiuorochloroethane. Theyield of 1,1,1-dif1uorochloroethane was about 8.4%.

Example 3 A feed gas mixture consisting of 111 parts of ethylidenefluoride and 100 parts of chlorine was fed continuously into the samereactor as in Example 2. The ethylidene fluoride and the chlorine werefed into the reactor at the respective 1,1,1-difluorochloroethane. was

' space velocity per hour.

rates of 0.00629 and 0.00528 cubic foot per minute, and rate of flow ofthe gas mixture thru the reactor was about 88 space velocity per hour.Molecular proportions of ethylidene fluoride to chlorine actually passedthru the reactor throughout the run were one to 0.84. The reaction wasexothermic, heat was generated, but no extraneous cooling was used. Thereacted gas mixture was continuously discharged from the reactor, andpurified as in Example 2. The second receiver was transferred to afractionating still, and the temperature of the liquid material wasraised to about minus 25 C. Overhead distillate was condensed and therewere recovered 11.3 parts of material having a boiling point of aboutminus 24-25 C., i.e. ethylidene fluoride. Temperature of the residualliquid in the still was then raised to about minus 10 C. Overheaddistillate was condensed and there were recovered 70.1 parts ofcondensate having a boiling point in the range of minus 9 to 10 C., i.e.1,1,1-difluorochloroethane. There remained in the still 13 parts ofhigher boiling fractions. The yield of 1,1,l-difluorocholoroethane wasabout 41%, about 47.2% by weight of the ethylidene fluoride input wasrecovered as reacted material, and of the reacted material recoveredabout 84.4% by weight was recovered as 1,1,-l-difluorochloroethane.

Example 4 A feed gas mixture consisting of 131 parts of ethylidenefluoride and 123 parts of chlorine was fed continuously into one end ofan annular reactor formed by a Pyrex glass jacket of 34 mm. insidediameter and 381 mm. length surrounding a 15 watt fluorescent light tubehaving an outside diameter of 26 mm. The reactor was provided with inletand outlet openings at opposite ends; had a volume of 144 cc., and thejacket was wrapped on the outside with aluminum foil. The ethylidenefluoride and the chlorine were fed into the reactor at the respectiverates of 0.00445 and 0.00392 cubic foot per minute, and rate of flow ofthe gas mixture thru the reactor was about 128 Molecular proportions ofethylidene fluoride to chlorine actually passed thru the reactorthroughout the run were one to 0.88. The reaction was exothermic, heatwas generated, but no extraneous cooling was used. The reacted gasmixture was continuously discharged from the reactor and was bubbledthru water to remove most of the HCl, then bubbled thru a caustic sodasolution of NaOH strength of about 20% to remove unreacted chlorine andthe last traces of H01, and the gas stream was thereafter dried bypassing the same thru a column of calcium chloride. Following theseoperations, the gas stream was passed into a receiver packed in amixture of dry ice and alittle acetone. Gaseous constituents of the gasstream were condensed at temperature of about minus 78 C. The receiverwas transferred to a fractionating still, and the temperature of theliquid material was raised to about minus 25 C. Overhead distillate wascondensed and there were recovered 19 parts of material having a boilingpoint of about minus 2425 C., i. e. ethylidene fluoride. Temperature ofthe residual liquid in the still was then raised to about minus 10 C.Overhead distillate was condensed, and there were recovered 132 parts ofcondensate having a boiling point in the range of minus 9 to 10 C., i.e. 1,1,1-difluorochloroethane. There remained in the still 12 parts ofhigher boiling fractions. The yield of about 66.4%,

about .71 ;by-.-weight;-of .ttherethylidene ifluoride inputiwasirecovered as :reacted: material, rand sof the .zreacted ..material:recovered ;about 91.7% :by weight :-.W3.S recovered as:1,'1,1'-'difluorochloroethane. Chlorine utilization .was :92

Example ,zA ieed gas mixture consisting; of.v 229 parts :ofethylideneifluoride and 249;:parts .of chlorine [was fed continuouslyinto one-.end;.of .the,,'reactor-of Example 4. The ethylidene fluoridegand the chlorine werev fed into gthe reactor. ,at-the: respective ratesof 0.01085 and 0.01085; cubic ,;foot .per minute, and rate of flowofathehgas mixturelthru theuireactor was about .256 space-velocity ,perhour. ,rriolecular.proportions ofeethylidene fluoride ;to chlorineactually passed vthru the --reactor-throughout therun werejone to.1.003.,The reaction was exothermic,- heatwasgenerated, but

no:.extraneouscoolingwasused. The reactedgas mixturewas continuouslydischarged from the reactor,,-and purified as in Example :4. Thereceiver was transferred to a -fractionatingstill, and the temperatureof the liquid material was raisedto about'minusq25" C.eOverheaddistillate was ,condensed and there were recovered 29.3parts-,ofimaterial havinga boiling point of about minus 24-25 .C.,;i.-,.e. ethylidene. fluoride. ,Temperature of the residual liquid in thestill was then raised to about minus" C. Overhead distillatewascondensed and there were recovered 254.5 partsof condensate having aboiling point inithe range of minus!) to"10'C., i. e."1,1;1-difluorochloroethane. "There remained inthestill 2853 parts ofhigherboiling fractions. 'Theyield of 1,1,1-difluorochloroethane wasabout 60%, about'66% by weight of the ethylidene fluoride input wasrecovered as reacted material, andof the reacted material recoveredabout 90.0% by weight was recovered as 1,1, -difluoroch1oroethane.Chlorine utilization was about 90%.

Example 1 6 A feed-gas mixture consisting of 1'35 l parts of ethylidenefluoride and 1654 parts of chlorine was fed continuousiydnto one end ofv the reactor of Example '4. The ethylidene fluoride and the chlorinewere ied'intothereactor at'theirespective rates of 0101020 and 0.01151cubio'foot per minute,"and rate of flow of the'gas'mixture thruthejreactor'was about Z56'space velocity per hour. Molecular proportionsof ethylidene fluoride to chlorine actually passed thru the reactorthroughout the run'were one to 1.13. The'reaction'was'exothermic, heatwas generated'but'no extraneous cooling was used. 'The'reacted gasmixture was continuously discharged from the reactor, and was bubbledtwice 'thru 'water to remove most of the HCl, then bubbled thru acausticsoda solution of NaOl-I strength of about ,toremove unreactedchlorine and the last traces of 'I-lCl, and the gas stream wasthereafter dried by passing the same thru a columnof calcium chloride.Following these operationsythe gasstream was passed intoa receiverpacked in a mixture of dry ice and a little acetone. 'Gaseousconstituents-oi the gas stream were condensed at-temperatureof--aboutmiuus 78 C. 'The receiver *wastransferred to a fractionating still, andthetemperature of the liquid material was raisedto about minus C.Overhead distillate was condensed and there were recovered 291 parts oimaterialhaving a boiling point of about minus"24-25 C., i. e.,ethylidene fluoride. Temperature of the residual liquid in thes'tillwasthen raisedtoabout minus 10.C. overheadp dis'tillateiwascondensedaandthere wererecovered1430 .parts ofzcondensate havingaxboiling point in therange of-tminus 9120.10? C.;,i..e.1,1,1-difluorochloroethane. .There remainedinthe still .212 .parts ofhigher boilingfiractions. The yield of 1,1,1-difluoro- .chloroethane wasabout 159.4% :about 77.1% by weight of the ethylidene. fluoride inputwas .recovered as reactedmaterial, and :of the reacted materialrecovered about .87.1.% was recovered as 1,1;1=difluoroch1oroethane.Chlorine; utilization was about 74.5%,

ExamYJZe 7 'A"feedigas mixture consisting of 550-parts of ethylidenefluorideand 617'parts of chlorine was fed continuously into one end *ofthe reactor of Example 4. The ethylidene fluoride and the chlorine werefed into the reactor at the respective rates of: 0.02204 and01022631011010. foot;per minute, and rate of flowbfsthe feed gasmixturethru' the reactor was-about 525 space velocity per.hour. 'Molecularproportions of ethylidene :fiuoride to chlorineactuallypassed thru thereactorthroughout the run -were'one-to.1.04. The reaction was exothermicheat-was generated, but'no extraneous cooling was used. Thereacted gasmixture was continuously discharged from the reactor, and was bubbledtwice thruwater to: remove most of theI-ICI, then bubbledthru a causticsoda solution of :NaOH strength of about 1 5% :to removeunreacted'chiorine and the last traces of HCl, and the -gas stream wasthereafter dried by passing the same thru a column of calcium'chloride.lfi ollowing these operations, I the gas stream was passed intoa'receiver packed in-a'mixture of: dry ice'and-a little acetone. Gaseousconstituents of the gas-stream-Were condensed at'temperature of aboutminus 78= C. The receiver wastransferred to ea Tractionating still, andthe temperature of the liquid -*material was raised -to about minus 25C. overhead distillate was-condensed and there-were-recovered.MiG-partsof material having a boiling point of about minus 2 1-25 0., i. e.ethylidene fiuoride. Temperature of the residual liquid-in the stillwasthen raised to abou-t minus 10 C. Overhead -'distil-late wascondensed and therewere-recovered 521 parts of condensate havin'g aboiling'point in the range of minus 9 to 10='C.,'i.- e. '1;1',ldifluorochloroethane. There remained in the-still 88 parts of higherboiling fractions. The y-ield of 1,1,l-difluorochloroethane was about60.2%,-about by weight of the ethylidene'fiuoride input was recovered asreacted material, and of -"the reacted material recovered about 85.6%icy-weight was recovered as 1,1;1-d-ifluorochloroethane. -"Ch-1orineutilization was about 74.5%.

"From the aboveexamples it will be noted that, under moderatelyfavorable operating conditions, the 'recovered'mixtures of reactedmaterials (1. e. the mixture "of reacted materials obtained afterremoval of unreact-ed ethylidene fluoride) containedby "weight fromabout 84% to about 92% of 1;1;1 difluorochloroethane, and that suchmixtures contained *by weight from about 16% to about 8% -of'higherboiling polychlorinated and other-undesired 'monochlorinated products.

We claim:

1. The process of preparing 1,1,1-difluoroch1oroethane which comprisescontinuously introducing ethylidene fluoride and :chlorine into areaction zone, regulating the amount of chlorine to :provide in "said.zone about: one molecular :proportion-of! chlorine,z.subj mating thematerial in said zone ;t o i-actinic :;radiation while .1ma'intainingiatemperature in the range from about room temperature to about 300 C. anda space velocity per hour in the range of 200-300, continuouslydischarging the resulting reaction mixture, and recovering a mixture ofreacted materials containing by weight not less than 80% of1,1,1-difiuorochloroethane.

2. The process which comprises subjecting a mixture of ethylidenefluoride and not substantially more than one molecular proportion ofchlorine to actinic radiation while maintaining a temperature in therange of from about room temperature to about 300 C. to thereby produce1,1,1-difluorochloroethane.

3. The process which comprises subjecting a mixture of ethylidenefluoride and about one molecular proportion of chlorine to actinicradiation while maintaining a temperature in the range of from aboutroom temperature to about 300 C. to thereby produce1,1,1-dif1uorochloroethane.

4. The process for preparing 1,1,l-difiuorochloroethane which comprisescontinuously introducing ethylidene fluoride with not substantially morethan one molecular proportion of chlorine into a reaction zone,subjecting the material therein to actinic radiation while maintaining atemperature in the range of from about room temperature to about 300 C.and a space velocity per hour not more than 600, continuouslydischarging the resulting reaction mixture from said zone, andrecovering 1,1,1-difluorochloroethane.

JOHN D. CALFEE. LEE B. SMITH.

REFERENCES CITED The following references are of record in the file ofthis patent:

Hass et al., Industrial and Engineering Chemistry, March 1936, pp.333-339.

Henne et al., Journal American Chemical Society, v01. 61 (1939), pp.938-940.

Henne et al., Journal American Chemical Society, vol. 63 (1941) pp.2692-94.

Henne et al., Journal American Chemical Society, vol. 64 (1942) pp.1157-59.

Henne et al., Journal American Chemical Society, vol. 6'7 (1945) pp.1906-8.

2. THE PROCESS WHICH COMPRISES SUBJECTING A MIXTURE OF ETHYLIDENEFLUORIDE AND NOT SUBSTANTIALLY MORE THAN ONE MOLECULAR PROPORTION OFCHLORINE TO ACTINIC RADIATION WHILE MAINTAINING A TEMPERATURE IN THERANGE OF FROM ABOUT ROOM TEMPERATURE TO ABOUT 300*C. TO THEREBY PRODUCE1,1,1-DIFLUOROCHLOROETHANE.